Dissertationen zum Thema „Render time“

Background. Games today are becoming more complex in computational andgraphical areas. Companies today want to develop games with state of the artgraphics while also having complicated and complex game logic. The vast majorityof users rarely meet the computer requirements. This creates an issue which lim-its the target demographic that a company wants to meet. This thesis will focuson two different methods that achieves deferred shading in Vulkan and how the en-vironment is affecting both methods as-well as the number of lights and attachments. Objectives. In Vulkan there are two ways of implementing deferred shading, one isthe traditional way of doing it which is by conducting multiple render-targets. Thesecond way is by utilizing a feature unique to Vulkan known as sub-passes. Our aimis to conduct experiments with these two ways of implementing deferred shading todetermine which one is the most optimal for a given situation. These situations willvary depending on the number of visible objects and number of lights in the scene. Methods. The experiments are conducted by a rendering system that have beenimplemented by us. By implementing both suggested deviations of the renderingtechnique ’deferred shading’ the data collected will suffer less from unexpected andunknown variables than it would if the implementations were taken from a separatesource. The experiments that will be conducted intend to measure performance met-rics in the form of average frames per second as well as average render frame time(inseconds). To measure the time performance metric, the system shall utilize Vulkan’ssupport for gpu-timestamping[7]. To provide reliable measurements without any un-warranted errors each rendering deviation will utilize pre-recorded command buffers. Conclusions. This thesis has shown that using multiple sub-passes within a singlerender-target performs faster write operations to the attached render attachments.This result in less memory bandwidth which leads to a faster geometry pass. Theperformance gain from a faster geometry pass can be used somewhere else to en-hance different aspects of the game or graphical application. Having less memorybandwidth would result in a longer battery life on mobile phones and laptops.

Background. In computer graphics, it can be a time-consuming process to render photorealistic images. This rendering process, called “physically based rendering” uses complex algorithms to calculate the behavior of light. Fortunately, most renderers offer the possibility to alter the render-settings, allowing for a decrease in render time, but this usually comes at the cost of a lower quality image. Objectives. This study aims to identify what setting has the highest impact on the rendering process in the V-Ray renderer. It also examines if a perceived difference can be seen when reducing this setting. Methods. To achieve this, an experiment was done where 22 participants would indicate their preference for rendered images. The images were rendered in V-Ray with different settings, which affected their respective render time differently. Additionally, an objective image metric was used to analyze the images and try to form a correlation with the subjective results. Results. The results show that the anti-aliasing setting had the highest impact on render time as well as user preference. It was found that participants preferred images with at least 25% to 50% anti-aliasing depending on the scene. The objective results also coincided well enough with the subjective results that it could be used as a faster analytical tool to measure the quality of a computer-generated image. Prior knowledge of rendering was also taken into account but did not give conclusive results about user preferences. Conclusions. From the results it can be concluded that anti-aliasing is the most important setting for achieving good subjective image quality in V-Ray. Additionally, the use of an objective image assessment tool can drastically speed up the process for targeting a specific visual quality goal.

Visualization is an important tool for making data understandable. Visualization can be used for many different purposes, such as charts on the web used to visualize a dataset. Render time is important for websites since slow response times can cause users to leave the site. When creating a website with fast render times in mind, the selection of JavaScript library may be crucial. This work aims to determine if dataset size and/or chart type affects the render time of charts created by different JavaScript libraries. The comparison is done by a literature search to identify suitable libraries, followed by an experiment in which 40 websites are created to compare the performance of selected JavaScript libraries for rendering selected chart types. The results show that while both dataset size and chart type affect the render time in most cases, the libraries scale differently depending on the dataset size.

Modelling and rendering natural phenomena, such as rain, is an important aspect of creating a realistic driving simulator. Rain is a crucial issue when driving in the real world as it for instance obstructs the driver’s vision. The difficulty is to implement it in a visually appealing way while simultaneously making it look realistic and keeping the computational cost low. In this report, a GPGPU (general-purpose computing on graphical processing units) based approach is presented where the final product is a rain simulation rendered onto a 2D texture, which can then be applied to a surface. The simulated raindrops interact with gravity, wind, a windshield wiper as well as with each other, and are then used to distort the background behind them in a convincing manner. The simulation takes into account multiple physical properties of raindrops and is shown to be suitable to run in real-time. The result is presented in form of a visual demonstration. In conclusion, even though the final simulation is still in its first iteration, it clearly highlights what can be accomplished by utilizing the GPU and the benefits of using a texture-based approach. The appropriate simulation approach will however always depend on the characteristics of the problem and the limitations of the hardware.

This is a presentation of the way I see the world created by mortals; these ideas shape my architectural perspective. The building is a museum designed to present a history of yachts: boats which present a way of building and a sensibility of materials. This consideration of the material used reveals each material’s characteristics in construction. Steel attenuates through optimization, and masonry becomes generous in form through the needs of its use. A building is a note emitted in a particular instant in the midst of a culture and composed of an infinitude of elements. Buildings measure mortal progress through the instrument of technology. Time is measured by matter. The building explores the rhythm and juxtaposition of elements in their relationships within the pattern of the building. The book is an examination of an order in text and images, given the technology i have chosen. The gathering of things that present meanings when juxtaposed begin to shape an idea, an emotion. Words as objects, gather to form complex ideas. In this book the transparent paper allows the presence of future images to influence present readings. To experience with the senses and the mind, we learn throughout existence giving order to our universe. Elements become multivalient by the continual layering of experience. Revisited in time, with fresh discovery in unselfconscious exploration things gain meaning. Culture evolved as its material record transforms.
Master of Architecture

Rendering takes time, especially without access to powerful hardware. Is there any way to reduce the time of rendering? With the help of compositing reducing the time of renders is very much possible, using a range of alternative methods. A total of three different approaches will be tested in order to save time, as well as trying to maintain quality as close to a render straight from a 3D application as possible. Projections using cards and geometry as well as deep data will be used in an attempt to find the most efficient and useful way of saving time.
Rendering tar tid, speciellt utan tillgång till kraftfull hårdvara. Finns det något sätt att dra ner på tiden en rendering tar? Med hjälp av compositing är det absolut möjligt att sänka tiderna för en rendering genom en rad alternativa metoder. Totalt kommer tre olika metoder att testas för att spara in tid, men även för att försöka komma så nära kvalitén av en bild renderad direkt från en 3D-appliaktion som möjligt. Projektioner på plan och geometri och användandet av deep-data kommer användas i ett försök att hitta det mest effektiva och användbara tillvägagångssättet att spara tid.

La métropole est polychronique. L'isolement d'un de ses rythmes permet de nuancer les théories de la modernité liquide et de la ville en continu. À travers l'étude de trois événements festifs métropolitains à Paris et Bruxelles, nous proposons une lecture de l'histoire urbaine par ses temps partagés, une description des mécanismes par lesquels les rythmes sociaux émergent et une analyse de leur rôle social et spatial. Réinterrogé par le concept de rendez-vous collectifs, les rythmes urbains sont une co-production entre un urbanisme temporaire et une urbanité événementielle. Ces deux éléments explique le double rôle spatial et social des rythmes événementiels. Les institutions municipales instrumentalisent l'urbanisme temporaire pour signifier le temps, organiser le rassemblement et produire du lieu. L'urbanité événementielle est le résultat des interprétations individuelles des événements comme signe temporel qui produit du lien social et un sens commun des lieux. La répétition de la rencontre entre l'urbanisme temporaire et l'urbanité événementielle provient d'une part, de la décision politique de d'instrumentaliser le rendez-vous dans l'organisation urbaine, d'autre part de la synchronisation des individus qui organisent leurs temps pour participer au rassemblement. La rationalité qui anime les participants est motivée par la valorisation des interactions de face-à-face et la production de liens sociaux associatifs, dans une société interrogée par la différenciation et la désynchronisation des modes de vie. L'individu ne se passe pas de rassemblements rituels, dans des lieux et selon des temporalités saisonnières. Ces rythmes collectifs sont adaptés à la métropole, à la complexification de ses territoires, à l'hybridation de ses représentations culturelles et à l'individualisation de ses temporalités. Au-delà, le concept de rythme est une théorie de morphologie sociale qui rend compte du fonctionnement des sociétés de façon multiscalaire et dynamique. Elle s'inscrit dans les théories sociologiques intermédiaires qui lient l'individu et le collectif, l'habitant et les institutions, la morphologie spatiale et temporelle de groupements humains de toutes tailles. Le fait métropolitain, influençant et influencé par l'individu et le global, constitue une échelle mésociale heuristique

The purpose of this research was to determine the effects of heating (including heating to ultra-high temperatures) homogenized ultrafiltered whole and skim milks on whey protein denaturation and milk's subsequent rennet coagulation properties: coagulation time, curd firmness, and microstructure. Whole and skim milk samples were ultrafiltered using a spiral wound ultrafiltration membrane system. Samples were preheated to 72°C for 58 s, held for 8 s then heated to 72, 89, 106, 123, or 140°C for more than 97 sand held for 4 s. The milk was then cooled to 60°C and homogenized, further cooled to 30°C, packaged into 120 ml sterile containers, and refrigerated overnight. Rennet coagulation time and curd firmness were monitored using a Formagraph . Milk and gel samples were fixed in 2.5% glutaraldehyde solution and examined by electron microscopy. Whey protein denaturation was determined by precipitating casein at pH 4.6 with .lN HCl and measuring protein content in the filtrate by the Kjeldahl procedure. Rennet coagulation time of milk increased as processing temperature was increased. Gel strength decreased with an increase in processing temperature. Ultrafiltration shortened rennet coagulation time and increased gel firmness. Ultra-high- temperature- heated whole and skim milks did not coagulate upon addition of rennet, but their concentrated counterparts did. Rennet coagulation of the concentrated milks was delayed by heating. Samples treated with ultra-high-temperature formed only a weak gel. The casein micelles in milk increased in size as a function of increasing processing temperature and concentration by ultrafiltration. Additional protein material adhered to the casein micelles after high-temperature processing and was especially noticeable in the samples treated with ultra-high-temperature. Whey protein denaturation increased as a function of increased heating temperature. The heated concentrated milks had higher levels of protein denaturation than the heated unconcentrated ones.

O presente trabalho tem como objetivo analisar a volatilidade dos mercados de renda fixa e renda variável no Brasil, no período de março de 1986 até fevereiro de 2006, por meio do CDI (Certificado de Depósito Interfinanceiro) e IRF-M (Índice de Renda Fixa de Mercado), como indicadores do mercado de renda fixa, e o IBOVESPA (Índice da BOVESPA), como indicador de renda variável. Por meio da comparação da volatilidade destes ativos é possível observar se há coincidência temporal entre os dois mercados, em relação aos picos de volatilidade devido, principalmente, a influência de variáveis macroeconômicas. Tal análise é importante para que os gestores de portfólios, que tomam decisões de como alocar os investimentos, conheçam o histórico e o corrente relacionamento entre as volatilidades dos dois mercados. As volatilidades do mercado de renda fixa e do mercado de renda variável foram calculadas por meio do desvio padrão anual dos retornos mensais e por meio de um modelo GARCH(1,1). Os resultados mostram que, no Brasil, durante o período analisado, os dois mercados apresentaram: períodos coincidentes de picos de volatilidade, grande mudança no padrão comportamental das volatilidades após a implantação do Plano Real e pouca estabilidade na relação entre as volatilidades.
This work aims to study the volatility of the fixed income market and the stock market in Brazil, from March 1986 to February 2006, through CDI (Interbank Interest Rate), IRF-M (Fixed Income Index), as a fixed income market indicators, and IBOVESPA (BOVESPA index), as a stock market indicator. Through the comparison of the volatility of these assets it is possible to observe if there is time frame coincidence between the two markets, in relation to the peaks of volatility due to, mainly the influence of macroeconomics variables. Such analysis is important so that portfolio managers, responsible for decisions such investments allocation, know the history and the actual relationship between the markets volatility. Such analysis is important so that portfolio managers, responsible for decisions such investments allocation, know the history and the actual relationship between the markets volatility. Those fixed income market and stock markets volatilities were calculated through the annual standard deviation of the monthly returns and from a GARCH(1,1) model. The results show that, in Brazil, during the studied period, both markets presents: coincident volatility peaks periods, high change in the behavioral pattern of volatility after the deployment of the Plano Real and little stability in the relationship between the volatility.

En informatique graphique, le rendu des matériaux occupe une place très importante dans la qualité de l’image finale. De nombreux modèles ont contribué à améliorer l’apparence des matériaux. Aujourd’hui, certains matériaux restent encore difficiles à représenter à cause de leur complexité. Parmi ceux ci,la famille des matériaux anisotropes reste peu étudiée et complexe. Dans cette thèse nous proposons une meilleure compréhension des matériaux anisotropes au travers d’un modèle pour les représenter ainsi qu’un outil permettant de mieux en contrôler l’apparence. Notre modèle de matériaux brossés ou rayés se base sur la simulation du transport lumineux au sein de la micro-géométrie d’une rayure pour restituer tous les détails en conservant des temps de rendus suffisamment courts pour rendre la scène de manière interactive.Notre outil d’édition des reflets anisotropes utilise le champ d’orientation des BRDF pour donner à l’utilisateur l’impression de dessiner ou de déformer des reflets directement sur l’objet
In computer graphics, material appearance is a fundamental component of the final image quality. Many models have contributed to improve material appearance. Today, some materials remains hard to represent because of their complexity. Among them, anisotopic materials are especially complex and little studied. In this thesis, we propose a better comprehension of anisotropic materials providing a representation model and an editing tool to control their appearance. Our scratched material model is based on a light transport simulation in the micro-geometry of a scratch, preserves all the details and keeps an interactive rendering time. Our anisotropic reflections edition tool uses BRDF orientation fields to give the user the impression to draw or deform reflections directly on the surface

Explorer et comprendre des données volumétriques ou surfaciques est un des nombreux enjeux du domaine de l'informatique graphique. L'apparence de telles données peut être modélisée et visualisée en utilisant la théorie du transport lumineux. Afin de rendre une telle visualisation compréhensible, le recours à des matériaux transparents est très répandu. Si des solutions existent pour simuler correctement la propagation de la lumière et ainsi afficher des objets semi-transparents, offrir une visualisation compréhensible reste un sujet de recherche ouvert. Le but de cette thèse est double. Tout d'abord, une analyse approfondie du modèle optique pour le transport de la lumière et ses implications sur la génération d'images par ordinateur doit être effectuée. Ensuite, cette connaissance pourra être utilisée pour proposer des solutions efficaces et fiables pour visualiser des milieux transparents et semi-transparents. Dans ce manuscrit, premièrement, nous présentons le modèle optique communément utilisé pour modéliser le transport de la lumière dans des milieux participatifs, sa simplification si l'on réduit la situation à des surfaces et la manière dont ces modèles sont utilisés en informatique graphique pour générer des images. Deuxièmement, nous présentons une solution pour améliorer la représentation des formes dans le cas particulier des surfaces. La technique proposée utilise le transport lumineux comme base pour modifier le processus d'éclairage et modifier l'apparence et l'opacité des matériaux. Troisièmement, nous nous concentrons sur la problématique de l’utilisation de données volumétriques au lieu du cas simplifié des surfaces. Dans ce cas, le fait de ne modifier que les propriétés du matériau a un impact limité. Nous étudions donc comment le transport lumineux peut être utilisé pour fournir des informations utiles à la compréhension de milieux participatifs. Enfin, nous présentons notre modèle de transport lumineux pour les milieux participatifs, qui vise à explorer une région d'intérêt d’un volume
Exploring and understanding volumetric or surface data is one of the challenges of Computer Graphics. The appearance of these data can be modeled and visualized using light transport theory. For the sake of understanding such a data visualization, transparent materials are widely used. If solutions exist to correctly simulate the light propagation and display semi-transparent objects, offering a understandable visualization remains an open research topic. The goal of this thesis is twofold. First, an in-depth analysis of the optical model for light transport and its implication on computer generated images is performed. Second, this knowledge can be used to tackle the problematic of providing efficient and reliable solution to visualize transparent and semi-transparent media. In this manuscript, we first introduce the general optical model for light transport in participating media, its simplification to surfaces, and how it is used in computer graphics to generate images. Second, we present a solution to improve shape depiction in the special case of surfaces. The proposed technique uses light transport as a basis to change the lighting process and modify the materials appearance and opacity. Third, we focus on the problematic of using full volumetric data instead of the simplified case of surfaces. In this case, changing only the material properties has a limited impact, thus we study how light transport can be used to provide useful information for participating media. Last, we present our light transport model for participating media that aims at exploring part of interest of a volume

Le but du rendu stylisé est de produire un rendud'une scène 3D dans le style visuel particuliervoulu par un artiste.Cela nécessite de reproduire automatiquementsur ordinateur certaines caractéristiquesd'illustrations traditionnelles: par exemple,la façon dont un artiste représente les ombres et lalumière, les contours des objets, ou bien les coupsde pinceau qui ont servi à créer une peinture.Les problématiques du rendu stylisé sont pertinentesdans des domaines comme la réalisation de films d'animation 3Dou le jeu vidéo, où les studios cherchent de plus en plus à se démarquerpar des styles visuels originaux.Dans cette thèse, nous explorons des techniques destylisation qui peuvent s'intégrer dans des pipelinesde rendu temps-réel existants, et nous proposons deux contributions.La première est un outil de création de modèles d'illuminationstylisés pour des objets 3D.La conception de ces modèles est complexe et coûteuse en temps,car ils doivent produire un résultat cohérentsous une multitude d'angles de vue et d'éclairages.Nous proposons une méthode qui facilite la créationde modèles d'illumination pour le rendu stylisé,en les décomposant en sous-modèles plus simples à manipuler.Notre seconde contribution est un pipeline de rendude scènes 3D dans un style peinture,qui utilise une combinaison de bruits procéduraux 3Det de filtrage en espace écran.Des techniques de filtrage d'image ont déjà été proposéespour styliser des images ou des vidéos:le but de ce travail est d'utiliser ces filtres pourstyliser des scènes 3D tout en gardant la cohérence du mouvement.Cependant, directement appliquer un filtreen espace écran produit des défauts visuels au niveau dessilhouettes des objets.Nous proposons une méthode qui permet d'assurer la cohérence du mouvement,en guidant les filtres d'images avec des informations sur la géométrie extraites de G-buffers, et qui élimine les défauts aux silhouettes
The goal of stylized rendering is to render 3D scenes in the visual style intended by an artist.This often entails reproducing, with some degree of automation,the visual features typically found in 2D illustrationsthat constitute the "style" of an artist.Examples of these features include the depiction of light and shade,the representation of the contours of objects,or the strokes on a canvas that make a painting.This field is relevant today in domains such as computer-generated animation orvideo games, where studios seek to differentiate themselveswith styles that deviate from photorealism.In this thesis, we explore stylization techniques that can be easilyinserted into existing real-time rendering pipelines, and propose two novel techniques in this domain.Our first contribution is a workflow that aims to facilitatethe design of complex stylized shading models for 3D objects.Designing a stylized shading model that follows artistic constraintsand stays consistent under a variety of lightingconditions and viewpoints is a difficult and time-consuming process.Specialized shading models intended for stylization existbut are still limited in the range of appearances and behaviors they can reproduce.We propose a way to build and experiment with complex shading modelsby combining several simple shading behaviors using a layered approach,which allows a more intuitive and efficient exploration of the design space of shading models.In our second contribution, we present a pipeline to render 3D scenes in painterly styles,simulating the appearance of brush strokes,using a combination of procedural noise andlocal image filtering in screen-space.Image filtering techniques can achieve a wide range of stylized effects on 2D pictures and video:our goal is to use those existing filtering techniques to stylize 3D scenes,in a way that is coherent with the underlying animation or camera movement.This is not a trivial process, as naive approaches to filtering in screen-spacecan introduce visual inconsistencies around the silhouette of objects.The proposed method ensures motion coherence by guiding filters with informationfrom G-buffers, and ensures a coherent stylization of silhouettes in a generic way

La représentation des phénomènes météorologiques est un enjeu essentiel en Informatique Graphique dans l’optique d’obtenir des scènes extérieures visuellement réalistes. Depuis quelques années, les chercheurs se sont penchés sur la simulation de la pluie en synthèse d’images. Ce mémoire a pour but de présenter deux méthodes de rendu : une première méthode pour le rendu de la pluie, et une seconde pour le rendu des égouttements provenant des arbres. Notre modèle de rendu de pluie est une méthode multi-échelle permettant de tenir compte des propriétés locales et globales de ce phénomène. Nous avons réussi à mettre en corrélation la densité des gouttes proches de l’observateur (échelle mésoscopique) avec l’atténuation de la visibilité (échelle macroscopique), en fonction d’un seul paramètre global cohérent : l’intensité des précipitations. Cette méthode a fait l’objet d’une publication [56] dans la revue Computers & Graphics en 2015. D’autre part, nous basons notre méthode pour le rendu des égouttements sur une approche phénoménologique. Une telle approche s’avère plus adaptée pour gérer les grands espaces, et présente l’avantage d’être indépendante de la complexité de la scène. L’approche choisie s’appuie sur des expérimentations et des mesures hydrologiques effectuées par des chercheurs spécialisés dans l’hydrologie des forêts. Nous proposons ainsi un modèle d’égouttement cohérent, tenant compte des propriétés intrinsèques à chaque type d’arbres. Cette méthode a fait elle aussi l’objet d’une présentation à la conférence Eurographics Symposium on Rendering (EGSR) ainsi qu’une publication [57] au journal Computer Graphics Forum (CGF) en 2016
This dissertation aims to present a coherent multiscale model for real-time rain rendering which takes into account local and global properties of rainy scenes. Our goal is to simulate visible rain streaks close to the camera as well as the progressive loss of visibility induced by atmospheric phenomena. Our model proposes to correlate the attenuation of visibility, which is due in part to the extinction phenomenon, and the distribution of raindrops in terms of rainfall intensity and camera's parameters. Furthermore, this method proposes an original rain streaks generation based on spectral analysis and sparse convolution theory. This allows an accurate control of rainfall intensity and streaks appearance, improving the global realism of rainy scenes. We also aim at rendering interactive visual effects inherent to complex interactions between trees and rain in real-time in order to increase the realism of natural rainy scenes. Such a complex phenomenon involves a great number of physical processes influenced by various interlinked factors and its rendering represents a thorough challenge in Computer Graphics. We approach this problem by introducing an original method to render drops dripping from leaves after interception of raindrops by foliage. Our method introduces a new hydrological model representing interactions between rain and foliage through a phenomenological approach. Our model reduces the complexity of the phenomenon by representing multiple dripping drops with a new fully functional form evaluated per-pixel on-the-fly and providing improved control over density and physical properties. Furthermore, an efficient real-time rendering scheme, taking full advantage of latest GPU hardware capabilities, allows the rendering of a large number of dripping drops even for complex scenes

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
Esta dissertaÃÃo à composta de trÃs artigos, sendo que cada um se torna um capÃtulo. No primeiro capÃtulo intitulado âRelaÃÃo entre Desigualdade de Renda e Crescimento EconÃmico no Brasilâ analisa-se esta relaÃÃo a partir da hipÃtese do U-invertido de Kuznets no perÃodo de 1995 a 2012. A suposiÃÃo do U-invertido â hipÃtese de Kuznets (1955) â alude, no curto prazo, que hà uma conexÃo positiva entre a desigualdade de renda e o nÃvel de renda per capita. Jà no longo prazo, percebe-se uma relaÃÃo de U-invertido, pois hà uma inversÃo desta relaÃÃo. Para tanto, utiliza-se um modelo de estimaÃÃo para dados em painel dinÃmico e o mÃtodo de estimaÃÃo empregado à o dos Momentos Generalizado-sistema (MMG-sistema), desenvolvido por Arellano-Bond (1991), Arellano-Bover (1995) e Blundell e Bond (1998). Dentre outros resultados, conclui-se que a hipÃtese de Kuznets à confirmada nos Estados brasileiros. Fundamentando-se nas teorias que procuram relacionar pobreza, desigualdade, crescimento econÃmico e bem estar, o capÃtulo dois tem por objetivo decompor a variaÃÃo da pobreza, baseando-se nos seguintes fatores: efeito tendÃncia, efeito crescimento, efeito desigualdade e efeito residual, para os estados brasileiros entre 2001 e 2012. Para isso, partiu-se da estimaÃÃo de um modelo estatÃstico com dados em painel, utilizando as variÃveis pobreza, renda familiar per capita e o coeficiente de Gini, extraÃdas da PNAD. Os resultados estimados do modelo permitem inferir que na maior parte dos estados, o efeito crescimento se sobressaiu em relaÃÃo aos demais em se tratando da explicaÃÃo da reduÃÃo da pobreza no perÃodo analisado. NÃo obstante, o efeito distribuiÃÃo tambÃm teve sua importÃncia nesse processo, seguido do efeito tendÃncia. PorÃm, o efeito residual foi de pouca relevÃncia. Assim, finalizando este trabalho, no capÃtulo trÃs realiza-se uma anÃlise da pobreza de tempo para o Brasil, tendo por parÃmetro o uso da alocaÃÃo do tempo como um indicador de bem estar, em que a pobreza de tempo à mensurada adaptando as medidas de pobreza de renda da classe Foster, Greer e Thorbecke (1984) â FGT, especificamente para a pobreza de tempo, utilizando como indicadores a proporÃÃo de pobres de tempo ( ), o hiato de pobreza de tempo que mede a sua intensidade ( ) e o hiato de pobreza de tempo ao quadrado que mensura sua severidade ( ). Com isso, parte-se da estimaÃÃo de um modelo estatÃstico com dados em painel, utilizando as variÃveis ârendimentos de todos os trabalhosâ, âidadeâ, âanos mÃdios de estudoâ para explicar a pobreza de tempo nos estados brasileiros. Os resultados encontrados indicam que havendo uma elevaÃÃo nos rendimentos, diminui-se a pobreza de tempo; quanto mais elevada for a idade do indivÃduo, maior a chance de ser pobre de tempo; e quanto maior o nÃvel de escolaridade das pessoas, maior serà sua privaÃÃo de tempo em detrimento aos de menor escolaridade.
This dissertation is composed by 3 papers which, where each paper is a dissertation chapter. This first chapter entitled âRelationship between wealth inequality and economic growth in Brazilâ analyses the relationship from Kuznets inverted U hypothesis from 1995 to 2012. The inverted U supposition â Kuznets hypothesis (1955) â deals, in short term, exists a positive connection among wealth inequality and the per capita income level. In the long term, we observe a inverted U relationship, because there is a inversion of this relation. Thus, we use dynamic panel model and the Generalized method of moments system estimation method, developed by Arellano-Bond (1991), Arellano-Bover(1995) and Blundell e Bond (1998). The results show that the Kuznets hypothesis was confirmed. Based in the theories which seek relates poverty, inequality, economic growth and welfare, the chapter two aims to decompose the poverty variation, basing in the following factors: trend effect, growth effect, inequality effect and residual effect, for Brazilian states between 2001 and 2012. To reach this objective, we estimated a statistic model with panel data, using poverty variables, per capita familiar income and gini coefficient, extracted from PNAD. The results estimated allow to infer which in the most of Brazilian states, the growth effect stood out in relation to another effects regarding the explanation of poverty reduction in the period analyzed. Nonetheless, the distribution effect too had its importance in this process, followed by trend effect. However, the residual effect had low explanation power. Thus, finishing this dissertation, the chapter three analyses the poverty time for Brazil, using indicators as ratio of poor in time ( ), the time poverty gap, which measures its intensity ( ) and the squared poverty time, who measures its severity ( ). Then, from estimation of statistical model with panel data, using the variables âall labor incomeâ, âageâ, average years of study to explain the poverty time in the Brazilian states. The results indicate the a increase in the income have been occurring, reducing the poverty in time; how much higher is the individual age, higher the chance of they being poverty in time; and, higher education level of people, greater their privation of time in comparison to people with lower education level.

This study aims to gather, analyze, and interpret the potential and economic feasibility of sequestering carbon dioxide and/or generating renewable energy from the processing of pig manure, via time series analysis, using the Box and Jenkins (1970) models for future prediction. Swine production systems generate large amounts of waste which are highly polluting and impact the environment, principally greenhouse gases. When treated, these gases produce methane gas and in turn biogas, which when removed correctly is converted into electricity and carbon credits, leaving behind a high quality biofertilizer. This scenario of carbon dioxide sequestration was only possible after the adoption of the Kyoto Protocol, which provides for the Clean Development Mechanism (CDM) and the sale of Certified Emission Reductions (CER); electrical energy was affected by Regulatory Resolution 482/ 2012 of the National Electric Energy Agency (ANEEL). Data were was gathered with the support of the Municipal Association of Swine Producers of Toledo (AMST) and the BRF Company. This study demonstrates that it is feasible to use biogas and that the payback period follows a production scale with equipment operating 10 hours or more daily. Consequently, the payback period will be between 70 and 80 months, with production of electrical energy and/or in conjunction with the production of carbon credits. The study also shows that the production volume is feasible and should accommodate a minimum number of pigs. In addition, prediction models are important tools since they anticipate the behavior of the series under study, providing support so that investments can be made, reducing risks to the both the swine producer (in the area of finances) and to the farm, as well as allowing for another source of income. By reducing production costs, autonomy is guaranteed in ensuring an uninterrupted supply of electricity, which is needed for swine operations which become more and more dependent on technology.
O presente estudo visa reunir, analisar e interpretar o potencial e a viabilidade econômica do sequestro de gás carbônico e/ou a geração de energia renovável proveniente do tratamento de dejetos suínos, por meio da análise de séries temporais, com utilização dos modelos de previsão Box e Jenkins (1970). Como os sistemas de produção de suínos geram grande quantidade de dejetos altamente poluentes e impactantes no meio ambiente, principalmente os gases de efeito estufa, estes, ao serem tratados, produzirão o gás metano e dentro deste o biogás que, ao ser eliminado corretamente é convertido em energia elétrica e em créditos de carbono, restando na propriedade um biofertilizante de alta qualidade. Cenário do sequestro de gás carbônico que só foi possível após a aprovação do Protocolo de Quioto que prevê o Mecanismo de Desenvolvimento Limpo (MDL), a comercialização dos Certificados de Emissões Reduzidas (CER) e, no âmbito da energia elétrica, pela Resolução Regulamentadora 482/2012 da Agência Nacional de Energia Elétrica (ANEEL). Para o levantamento dessas informações, contou-se com o apoio da Associação Municipal dos Suinocultores de Toledo (AMST) e da Empresa BRF. Esta pesquisa demonstra que é viável a utilização do biogás e que o período de retorno obedece a uma escala de produção com um funcionamento diário dos equipamentos de 10 horas ou mais. Dessa forma, o período do retorno do investimento será entre 70 a 80 meses, com a produção de energia elétrica e/ou em conjunto com a produção de créditos de carbono. Mostra também que o volume de produção é viável, desde que aloje um número mínimo de suínos. Além disso, o uso de modelos de previsão é importante ferramenta, pois antecipam o comportamento da série em estudo, fornecendo ao produtor subsídios para que o investimento seja feito reduzindo o risco ao suinocultor, tanto nos aspectos financeiros, pois a granja terá mais uma fonte de renda, quanto na redução dos custos de produção, já que terá autonomia no fornecimento de energia elétrica ininterruptamente, o que é necessário nos sistemas de criação cada vez mais tecnificados.

La synthèse de textures est une technique qui génère une texture automatiquement grâce à un algorithme. Cette technique permet de réduire le temps de création des textures et le coût mémoire étant donné que seuls les algorithmes et leurs paramètres ont besoin d'être stockés. Cependant, des difficultés sont souvent rencontrées lors de l'utilisation des textures synthétisées. D'abord, les paramètres de ces textures sont difficiles à manipuler. Ensuite, l'algorithme de synthèse génère souvent les textures sous forme de tableaux de pixels nécessitant beaucoup de mémoire. Pour aborder ces difficultés, nous proposons les approches suivantes : pour améliorer la visualisation de l'espace des textures synthétisées, nous proposons de construire un résumé de cet espace: une seule image statique qui résume, dans un espace limité de pixels, les apparences produites par un synthétiseur donné. De plus, pour améliorer la sélection de paramètres, nous augmentons les curseurs qui contrôlent les paramètres avec des bandes visuelles révélant les changements qui se produisent quand l'utilisateur manipule les curseurs. Pour permettre à l'utilisateur d'interagir de manière interactive avec les résumés visuels, nous nous reposons sur un algorithme de synthèse par patch permettant de générer les textures de façon rapide grâce à une implémentation parallèle sur le processeur graphique. Au lieu de générer le résultat de ce synthétiseur sous forme d'un tableau de pixels, nous représentons le résultat dans une structure compacte et nous utilisons une méthode rapide permettant de lire des pixels directement à partir de cette structure
Texture synthesis is a technique that algorithmically generates textures at rendering time. The automatic synthesis reduces authoring time and memory requirements since only the algorithm and its parameters need to be stored or transferred. However, two difficulties often arise when using texture synthesis: First, the visualization and parameters selection of synthesized textures are difficult. Second, most synthesizers generate textures in a bitmap format leading to high memory usage. To address these difficulties we propose the following approaches: First, to improve the visualization of synthesized textures we propose the idea of a procedural texture preview: A single static image summarizing in a limited pixel space the appearances produced by a given synthesizer. The main challenge is to ensure that most appearances are visible, are allotted a similar pixel area, and are ordered in a smooth manner throughout the preview. Furthermore, to improve parameters selection we augment sliders controlling parameters with visual previews revealing the changes that will be introduced upon manipulation. Second, to allow user interactions with these visual previews we rely on a fast patch-based synthesizer. This synthesizer achieves a high degree of parallelism and is implemented entirely on the GPU. Finally, rather than generating the output of the synthesizer as a bitmap texture we encode the result in a compact representation and allow to decoding texels from this representation during rendering

Au cours des deux dernières décennies, les applications temps réel ont montré des améliorations colossales dans la génération de rendus photoréalistes. Cela est principalement dû à la disponibilité de modèles 3D avec une quantité croissante de détails. L'approche traditionnelle pour représenter et visualiser des objets 3D hautement détaillés est de les décomposer en un maillage basse fréquence et une carte de déplacement encodant les détails. La tessellation matérielle est le support idéal pour implémenter un rendu efficace de cette représentation. Dans ce contexte, nous proposons une méthode générale pour la génération et le rendu de maillages multi-résolutions compatibles avec la tessellation matérielle. Tout d'abord, nous introduisons une métrique dépendant de la vue capturant à la fois les distorsions géométriques et paramétriques, permettant de sélectionner la le niveau de résolution approprié au moment du rendu. Deuxièmement, nous présentons une nouvelle représentation hiérarchique permettant d'une part des transitions temporelles et spatiales continues entre les niveaux et d'autre part une tessellation matérielle non uniforme. Enfin, nous élaborons un processus de simplification pour générer notre représentation hiérarchique tout en minimisant notre métrique d'erreur. Notre méthode conduit à d'énormes améliorations tant en termes du nombre de triangles affiché qu'en temps de rendu par rapport aux méthodes alternatives
In the last two decades, real-time applications have exhibited colossal improvements in the generation of photo-realistic images. This is mainly due to the availability of 3D models with an increasing amount of details. Currently, the traditional approach to represent and visualize highly detailed 3D objects is to decompose them into a low-frequency mesh and a displacement map encoding the details. The hardware tessellation is the ideal support to implement an efficient rendering of this representation. In this context, we propose a general framework for the generation and the rendering of multi-resolution feature-aware meshes compatible with hardware tessellation. First, we introduce a view-dependent metric capturing both geometric and parametric distortions, allowing to select the appropriate resolution at rendertime. Second, we present a novel hierarchical representation enabling on the one hand smooth temporal and spatial transitions between levels and on the other hand a non-uniform hardware tessellation. Last, we devise a simplification process to generate our hierarchical representation while minimizing our error metric. Our framework leads to huge improvements both in terms of triangle count and rendering time in comparison to alternative methods

Les travaux proposés dans cette thèse s’intéressent à la commande et la surveillance d’une classe particulière de systèmes de production : les systèmes manufacturiers à contraintes de temps de séjour. Nous supposons dans l'étude que les ressources ont déjà été affectées et que l'ordre des opérations est déjà fixé par le module de planification/ordonnancement. Les hypothèses de fonctionnement répétitif avec et sans postes d'assemblage sont adoptées. De manière assez classique pour ce type de problématique, le formalisme utilisé est celui des Réseaux de Petri P-temporels pour l'étude des instants de débuts et de fins des opérations.Une étude de la robustesse des ateliers manufacturiers à contraintes de temps a été développée. La robustesse est abordée avec et sans modification de la commande relative à la robustesse active et à la robustesse passive respectivement, face aux perturbations temporelles. Un algorithme de calcul d'une borne supérieure de la robustesse passive est présenté. De plus, trois stratégies de commande robuste face aux perturbations temporelles ont été développées.Par ailleurs, l’incertitude dans les systèmes de production manufacturière à été étudié. Notre contribution dans ce cadre porte sur l’intégration des résultats concernant la robustesse dans la génération de symptômes et la classification des comptes rendus associés aux différentes opérations en utilisant la logique floue.Partant d’un système commandé, nous avons présenté en détail une démarche à suivre pour la mise en œuvre d’un modèle de surveillance en se basant sur les chroniques et les arbres de défaillance flous. Cette démarche est appliquée à un atelier de production laitière
The works proposed in this thesis are interested in controlling and monitoring of a particular class of production system : manufacturing job-shops with time constraints. We suppose in the study that the resources are allocated and the operations order is fixed by the module of planning/scheduling. The assumptions of repetitive functioning mode with and without assembling tasks are adopted. For this type of problems, the formalism of P-time Petri nets is used in order to study the operations time constraints.A study of the robustness of the manufacturing workshop to time constraints, has been developed. The robustness is approached with and without control reaction qualified as active robustness and passive robustness respectively, towards time disturbances. A computing algorithm of the upper bound of the passive robustness is presented. In addition, three robust control strategies facing time disturbances were developed.Furthermore, uncertainty in manufacturing systems has been studied. Our contribution in this context is by integration of the analytical knowledge of the robustness in the filtering mechanism of sensors signals that are associated to operations, by using fuzzy logic.Starting from a controlled system, we have presented in detail, a method to be followed for the implementation of a monitoring model based on the chronicles and fuzzy fault tree analysis. This approach is applied to a milk production unit

Cette thèse traite de la modélisation, l'illumination et le rendu temps-réel de milieux participants à l'aide du GPU. Dans une première partie, nous commençons par développer une méthode de rendu de nappes de brouillard hétérogènes pour des scènes en extérieur. Le brouillard est modélisé horizontalement dans une base 2D de fonctions de Haar ou de fonctions B-Spline linéaires ou quadratiques, dont les coefficients peuvent être chargés depuis une textit{fogmap}, soit une carte de densité en niveaux de gris. Afin de donner au brouillard son épaisseur verticale, celui-ci est doté d'un coefficient d'atténuation en fonction de l'altitude, utilisé pour paramétrer la rapidité avec laquelle la densité diminue avec la distance au milieu selon l'axe Y. Afin de préparer le rendu temps-réel, nous appliquons une transformée en ondelettes sur la carte de densité du brouillard, afin d'en extraire une approximation grossière (base de fonctions B-Spline) et une série de couches de détails (bases d'ondelettes B-Spline), classés par fréquence.%Les détails sont ainsi classés selon leur fréquence et, additionnées, permettent de retrouver la carte de densité d'origine. Chacune de ces bases de fonctions 2D s'apparente à une grille de coefficients. Lors du rendu sur GPU, chacune de ces grilles est traversée pas à pas, case par case, depuis l'observateur jusqu'à la plus proche surface solide. Grâce à notre séparation des différentes fréquences de détails lors des pré-calculs, nous pouvons optimiser le rendu en ne visualisant que les détails les plus contributifs visuellement en avortant notre parcours de grille à une distance variable selon la fréquence. Nous présentons ensuite d'autres travaux concernant ce même type de brouillard : l'utilisation de la transformée en ondelettes pour représenter sa densité via une grille non-uniforme, la génération automatique de cartes de densité et son animation à base de fractales, et enfin un début d'illumination temps-réel du brouillard en simple diffusion. Dans une seconde partie, nous nous intéressons à la modélisation, l'illumination en simple diffusion et au rendu temps-réel de fumée (sans simulation physique) sur GPU. Notre méthode s'inspire des Light Propagation Volumes (volume de propagation de lumière), une technique à l'origine uniquement destinée à la propagation de la lumière indirecte de manière complètement diffuse, après un premier rebond sur la géométrie. Nous l'adaptons pour l'éclairage direct, et l'illumination des surfaces et milieux participants en simple diffusion. Le milieu est fourni sous forme d'un ensemble de bases radiales (blobs), puis est transformé en un ensemble de voxels, ainsi que les surfaces solides, de manière à disposer d'une représentation commune. Par analogie aux LPV, nous introduisons un Occlusion Propagation Volume, dont nous nous servons, pour calculer l'intégrale de la densité optique entre chaque source et chaque autre cellule contenant soit un voxel du milieu, soit un voxel issu d'une surface. Cette étape est intégrée à la boucle de rendu, ce qui permet d'animer le milieu participant ainsi que les sources de lumière sans contrainte particulière. Nous simulons tous types d'ombres : dues au milieu ou aux surfaces, projetées sur le milieu ou les surfaces

L'émergence des périphériques de capture numériques ont permis le dé- veloppement de l'acquisition 3D pour numériser les propriétés d'un objet réel : sa forme et son apparence. Ce processus fournit une représentation dense et précise d'objets réels et permet de s'abstraire d'un processus de simulation physique coûteux pour modéliser un objet. Ainsi, les problématiques ont évolué et portent non plus uniquement sur la modélisation des caractéristiques d'un objet réel mais sur les traitements de données issues de l'acquisition pour intégrer une copie de la réalité dans un processus de synthèse d'images. Dans ces travaux de thèse, nous proposons de nouvelles représentations pour des fonctions d'apparence issues de l'acquisition dont le but est de dénir un ensemble de modèles multi-échelles, de faible complexité en taille, capable d'être visualisé en temps réel sur le matériel graphique actuel.

L'un des objectifs lors du développement d'un produit industriel est d'obtenir un prototype numérique valide et réaliste. Cette thèse a pour objectif d'améliorer la qualité des simulations dans le contexte d'un processus de production. Ces processus impliquent souvent un rendu de type "walkthrough", avec une géométrie fixe mais un déplacement continu de l'observateur. Nous nous intéresserons donc plus précisément aux méthodes de rendu physiquement réaliste de scènes complexes pour un scénario "walkthrough". Durant le rendu, l'utilisateur doit pouvoir mesurer précisément la radiance d'un point ou d'une zone donnée, ainsi que modifier en temps réel la puissance des sources lumineuses. Fondée sur la méthode du photon mapping, nos travaux montrent les modifications à apporter aux algorithmes afin d'améliorer à la fois la qualité des images et le temps de calcul du processus de rendu
One of the goals when developing the product is to immediately obtain a real and valid prototype. This thesis provide new rendering methods to increase the quality of the simulations during the upstream work of the production pipeline. The latter usually requires a walkthrough rendering. Thus, we focuses on the physically-based rendering methods of complex scenes in walkthrough. During the rendering, the end-users must be able to measure the illuminate rates and to interactively modify the power of the light source to test different lighting ambiances. Based on the original photon mapping method, our work shows how some modifications can decrease the calculation time and improve the quality of the resulting images according to this specific context

O objetivo central desta tese foi o de testar a hipótese de que o custo de oportunidade do tempo da mulher brasileira, afeta positivamente o consumo de alimentos de fácil e rápido preparo e negativamente, o consumo dos alimentos “tempo intensivos”. Os dados utilizados no estudo são oriundos da Pesquisa de Orçamentos Familiares - (POF) 2002-2003, realizada pelo Instituto Brasileiro de Geografia e Estatística – IBGE. Foram utilizados tanto os microdados quanto as publicações da referida pesquisa. Com base na Teoria da Produção Domiciliar, e por meio da utilização de um modelo econométrico – o procedimento em dois estágios de Heckman, buscou-se avaliar a influência do custo de oportunidade do tempo da mulher e de alguns outros fatores como: o nível de renda domiciliar, a composição familiar, a urbanização entre outros, sobre o consumo domiciliar de um grupo selecionado de alimentos – feijão, arroz, batata, mandioca, carnes, farinha de trigo, alimentos prontos, pão, iogurte e refrigerantes e sucos – e sobre o consumo de alimentação fora do domicílio. Os principais resultados mostram que houve uma significativa mudança nos padrões de consumo alimentar das famílias brasileiras desde a década de 1970. Como exemplo cita-se a redução de 46% no consumo domiciliar de arroz polido e 37% no consumo de feijão e, um aumento de 490% no consumo de refrigerantes de guaraná e 216% de alimentos preparados. Os principais indicadores socioeconômicos dão conta de uma intensificação no processo de urbanização no Brasil, ou seja, atualmente 83% da população brasileira vive em áreas urbanas, enquanto em 1970 esse percentual era de apenas 56%. Além disso, 54% das mulheres brasileiras, que são chefe de família ou cônjuges, trabalham e 26% dos chefes de família hoje no Brasil são mulheres. No que se refere aos fatores que afetam os padrões de consumo, verificou-se que, o custo de oportunidade do tempo da mulher, está diretamente relacionado a um aumento na probabilidade de consumo e no gasto domiciliar com os alimentos que demandam um menor tempo de preparo, como por exemplo, os alimentos prontos, o pão, refrigerantes e sucos, iogurtes e alimentação fora do domicílio e, uma redução, tanto na probabilidade de consumo quanto no gasto familiar, com os “alimentos tradicionais”, feijão, arroz, mandioca, carnes e farinha de trigo que, em geral, demandam um maior tempo de preparo. Todas as variáveis, custo de oportunidade do tempo da mulher, nível de renda, urbanização e composição familiar, foram altamente significativas e importantes na determinação dos padrões de consumo de alimentos no Brasil.
The main objective of this thesis was to test the hypothesis that the woman’s opportunity costs of time affects positively the consumption of foods that are easy and quick to prepare and negatively the consumption of foods that are time intensive. This study uses micro data from the “Pesquisa de Orçamentos Familiares” - Family Budget Research (POF) 2002- 2003, carried out by the “Instituto Brasileiro de Geografia e Estatística” – IBGE – the Brazilian Institute of Geography and Statistics. Based on the theory of Household Production and making use of an econometric model – Heckman two stages procedure, it was aimed to evaluate the influence of the woman’s opportunity costs of time and other factors such as the level of household income, the family formation, urbanization, among others, on the household consumption of a distinct group of foods – bean, rice, potato, cassava, meat, wheat flour, readymade foods, bread, yogurt, soft drinks and juices - and on the consumption of foods eaten outside the home. The main results show that there has been a significant change in the standards of eating habits of the Brazilian families since the 1970’s. As an example, it was cited the reduction of 46% in household rice consumption and 37% in the bean consumption and, an increase of 490% in the soft drinks consumption and 216% in the ready-made foods. The main socioeconomic indicators show intensification in the urbanization process in Brazil, that is, currently 83% of the Brazilian population lives in urban areas, while in 1970 this percentage was only 56%. Besides that, 54% of the Brazilian women that are the head of the family or spouse are working and 26% of the heads of families in Brazil nowadays are women. As for the factors that affect the standards of consumption, it was verified that the woman’s opportunity cost of time is directly related to an increase in the probability of consumption and of the household expenses on foods that demand a shorter time to be prepared, for example, the ready-made foods, bread, soft drinks and juices, yogurt and foods eaten outside the home and, to a reduction, in the probability of consumption as well as in the household expenses, on “traditional foods” such as bean, rice, cassava, meat and wheat flour that, in general, demand a longer time to prepare. All the variables, woman’s opportunity costs of time, income level, urbanization and family formation were highly significant and important to determine the standards of food consumption in Brazil.

La technique de moyennation est un moyen efficace pour simplifier les transferts optimaux pour un satellite à faible poussée dans un problème à deux corps contrôlé. Cette thèse est une étude analytique et numérique du transferts orbital à poussée faible en temps optimal qui généralise l'application de la moyennation du problème à deux corps à des transferts dans le problème à deux corps perturbés et aux transfert d'une orbite proche de la Terre au point de Lagrange L1, dans le cadre du problème à quatre corps bi-circulaire où l’effet perturbatif de la Lune et du Soleil est modélisé. Dans le transfert à faible poussée à deux corps, nous comparons le cas du temps minimal et de l'énergie. Nous déterminons que le domaine elliptique pour les transferts orbitaux temps-minimal est géodésiquement convexe pour un transfert coplanaire et vers une orbite circulaire, contrairement au cas de l’énergie. Nous examinons ensuite l’effet la perturbation lunaire, nous montrons que dans ce cas le Hamiltonien moyenné se trouve être celui associé à un problème de navigation de Zermelo. Nous étudions numériquement à l’aide du code Hampath, les points conjugués pour caractériser l’optimalité globale des trajectoires. Enfin, nous construisons et réalisons numériquement un transfert d'une orbite terrestre au point de Lagrange L1, qui utilise la moyennation sur un arc (proche de la Terre) pour simplifier les calculs numériques. Dans ce dernier résultat nous voyons qu'un transfert concaténant une trajectoire moyennée avec une trajectoire temps minimal au voisinage du point de Lagrange est en effet proche d’un transfert de temps optimal calculé avec une méthode numérique de tir
The technique of averaging is an effective way to simplify optimal low-thrust satellite transfers in a controlled two-body Kepler problem. This study takes the form of both an analytical and numerical investigation of low-thrust time-optimal transfers, extending the application of averaging from the two-body problem to transfers in the perturbed low-thrust two body problem and a low-thrust transfer from Earth orbit to the L1 Lagrange point in the bicircular four-body setting. In the low-thrust two-body transfer, we compare the time-minimal case with the energy-minimal case, and determine that the elliptic domain under time-minimal orbital transfers (reduced in some sense) is geodesically convex. We then consider the Lunar perturbation of an energy-minimal low-thrust satellite transfer, finding a representation of the optimal Hamiltonian that relates the problem to a Zermelo navigation problem and making a numerical study of the conjugate points. Finally, we construct and implement numerically a transfer from an Earth orbit to the L1 Lagrange point, using averaging on one (near-Earth) arc in order to simplify analytic and numerical computations. In this last result we see that such a `time-optimal' transfer is indeed comparable to a true time-optimal transfer (without averaging) in these coordinates

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Nesse trabalho serão analisados possíveis impactos das mudanças de cidades de equipes da NFL durante a década de 90 e início dos anos 2000. Foram analisados dados de renda e emprego dessas regiões e a existência ou não de impacto econômico virá da análise do comportamento das variáveis após a mudança da equipe para a nova cidade. Será utilizado a metodologia ArCo desenvolvido em Carvalho, Masini e Medeiros (2018). Foi encontrada uma grande bibliografia de estudos de impactos econômicos gerados pela prática profissional esportiva em regiões, sempre associando os benefícios concedidos pelo governo com o benefício econômico gerado pela mudança ou chegada de uma equipe profissional a uma região. Esse trabalho se difere dos demais pois em nenhum deles há a aplicação de um modelo contra factual, ou seja, a abordagem desse trabalho será a primeira a tentar evidenciar impactos econômicos após a chegada de equipes profissionais esportivas utilizando esse tipo de modelo estatístico. Não foram encontrados efeitos nas variáveis e regiões estudadas nesse trabalho da prática profissional esportiva em uma região.
The present project aims at analyzing possible impacts from changes in the base-city of NFL teams during the period comprising from 1990 to the early 21th century. Data regarding employment rate and income in those regions would be the main basis of the diagnosis. Therefore, a detailed analysis of the behavior of these variables after the moment of the move from the team to a new town would reveal whether there was an economic impact. The model applied would be the ArCo, developed in Carvalho, Masini e Medeiros (2018). There is an extensive biography available regarding studies related to economic impacts generated by professional sports’ practice in specific regions, always associating the benefits granted by the government with the economic benefit generated by the arrival or departure of a professional team to that region. However, this work significantly differs from the others because in none of them there is the application of a counterfactual model. Therefore, the approach of the present work will be the first one to attempt at demonstrating the economic impacts after the arrival of professional sports teams using this type of statistical model. Author did not found relevant economic effects in variables that were analyzed in this study.

Uma grande dificuldade da gestão financeira é conseguir associar métodos quantitativos às formas tradicionais de gestão, em um único arranjo. O estilo tradicional de gestão tende a não crer, na devida medida, que métodos quantitativos sejam capazes de captar toda sua visão e experiência, ao passo que analistas quantitativos tendem a subestimar a importância do enfoque tradicional, gerando flagrante desarmonia e ineficiência na análise de risco. Um modelo que se propõe a diminuir a distância entre essas visões é o modelo Black-Litterman. Mais especificamente, propõe-se a diminuir os problemas enfrentados na aplicação da teoria moderna de carteiras e, em particular, os decorrentes da aplicação do modelo de Markowitz. O modelo de Markowitz constitui a base da teoria de carteiras há mais de meio século, desde a publicação do artigo Portfolio Selection [Mar52], entretanto, apesar do papel de destaque da abordagem média-variância para o meio acadêmico, várias dificuldades aparecem quando se tenta utilizá-lo na prática, e talvez, por esta razão, seu impacto no mundo dos investimentos tem sido bastante limitado. Apesar das desvantagens na utilização do modelo de média-variância de Markowitz, a idéia de maximizar o retorno, para um dado nível de risco é tão atraente para investidores, que a busca por modelos com melhor comportamento continuou e é neste contexto que o modelo Black-Litterman surgiu. Em 1992, Fischer Black e Robert Litterman publicam o artigo Portfolio Optimization [Bla92], fazendo considerações sobre o papel de pouco destaque da alocação quantitativa de ativos, e lançam o modelo conhecido por Black-Litterman. Uma grande diferença entre o modelo Black-Litterman e um modelo média-variância tradicional é que, enquanto o segundo gera pesos em uma carteira a partir de um processo de otimização, o modelo Black-Litterman parte de uma carteira de mercado em equilíbrio de longo prazo (CAPM). Outro ponto de destaque do modelo é ser capaz de fornecer uma maneira clara para que investidores possam expressar suas visões de curto prazo e, mais importante, fornece uma estrutura para combinar de forma consistente a informação do equilíbrio de longo prazo (priori) com a visão do investidor (curto prazo), gerando um conjunto de retornos esperados, a partir do qual os pesos em cada ativo são fornecidos. Para a escolha do método de estimação dos parâmetros, levou-se em consideração o fato de que matrizes de grande dimensão têm um papel importante na avaliação de investimentos, uma vez que o risco de uma carteira é fundamentalmente determinado pela matriz de covariância de seus ativos. Levou-se também em consideração que seria desejável utilizar um modelo flexível ao aumento do número de ativos. Um modelo capaz de cumprir este papel é o GARCH ortogonal, pois este pode gerar matrizes de covariâncias do modelo original a partir de algumas poucas volatilidades univariadas, sendo, portanto, um método computacionalmente bastante simples. De fato, as variâncias e correlações são transformações de duas ou três variâncias de fatores ortogonais obtidas pela estimação GARCH. Os fatores ortogonais são obtidos por componentes principais. A decomposição da variância do sistema em fatores de risco permite quantificar a variabilidade que cada fator de risco traz, o que é de grande relevância, pois o gestor de risco poderá direcionar mais facilmente sua atenção para os fatores mais relevantes. Ressalta-se também que a ideia central da ortogonalização é utilizar um espaço reduzido de componentes. Neste modelo de dimensão reduzida, suficientes fatores de risco serão considerados, assim, os demais movimentos, ou seja, aqueles não capturados por estes fatores, serão considerados ruídos insignificantes para este sistema. Não obstante, a precisão, ao desconsiderar algumas componentes, irá depender de o número de componentes principais ser suficiente para explicar grande parte da variação do sistema. Logo, o método funcionará melhor quando a análise de componentes principais funcionar melhor, ou seja, em estruturas a termo e outros sistemas altamente correlacionados. Cabe mencionar que o GARCH ortogonal continua igualmente útil e viável quando pretende-se gerar matriz de covariâncias de fatores de risco distintos, isto é, tanto dos altamente correlacionados, quanto daqueles pouco correlacionados. Neste caso, basta realizar a análise de componentes principais em grupos correlacionados. Feito isto, obtêm-se as matrizes de covariâncias utilizando a estimação GARCH. Em seguida faz-se a combinação de todas as matrizes de covariâncias, gerando a matriz de covariâncias do sistema original. A estimação GARCH foi escolhida pois esta é capaz de captar os principais fatos estilizados que caracterizam séries temporais financeiras. Entende-se por fatos estilizados padrões estatísticos observados empiricamente, que, acredita-se serem comuns a um grande número de séries temporais. Séries financeiras com suficiente alta frequência (observações intraday e diárias) costumam apresentar tais características. Este modelo foi utilizado para a estimação dos retornos e, com isso, obtivemos todas as estimativas para que, com o modelo B-L, pudéssemos gerar uma carteira ótima em um instante de tempo inicial. Em seguida, faremos previsões, obtendo carteiras para as semanas seguintes. Por fim, mostraremos que a associação do modelo B-L e da estimação GARCH ortogonal pode gerar resultados bastante satisfatórios e, ao mesmo tempo, manter o modelo simples e gerar resultados coerentes com a intuição. Este estudo se dará sobre retornos de títulos de renda fixa, mais especificamente, títulos emitidos pelo Tesouro Nacional no mercado brasileiro. Tanto a escolha do modelo B-L, quanto a escolha por utilizar uma carteira de títulos emitidos pelo Tesouro Nacional tiveram como motivação o objetivo de aproximar ferramentas estatísticas de aplicações em finanças, em particular, títulos públicos federais emitidos em mercado, que têm se tornado cada vez mais familiares aos investidores pessoas físicas, sobretudo através do programa Tesouro Direto. Ao fazê-lo, espera-se que este estudo traga informações úteis tanto para investidores, quanto para gestores de dívida, uma vez que o modelo média-variância presta-se tanto àqueles que adquirem títulos, buscando, portanto, maximizar retorno para um dado nível de risco, quanto para aqueles que emitem títulos, e que, portanto, buscam reduzir seus custos de emissão a níveis prudenciais de risco.
One major challenge to financial management resides in associating traditional management with quantitative methods. Traditional managers tend to be skeptical about the quantitative methods contributions, whereas quantitative analysts tend to disregard the importance of the traditional view, creating clear disharmony and inefficiency in the risk management process. A model that seeks to diminish the distance between these two views is the Black-Litterman model (BLM). More specifically, it comes as a solution to difficulties faced when using modern portfolio in practice, particularly those derived from the usage of the Markowitz model. Although the Markowitz model has constituted the basis of portfolio theory for over half century, since the publication of the article Portfolio Selection [Mar52], its impact on the investment world has been quite limited. The Markowitz model addresses the most central objectives of an investment: maximizing the expected return, for a given level of risk. Even though it has had a standout role in the mean-average approach to academics, several difficulties arise when one attempts to make use of it in practice. Despite the disadvantages of its practical usage, the idea of maximizing the return for a given level of risk is so appealing to investors, that the search for models with better behavior continued, and is in this context that the Black-Litterman model came out. In 1992, Fischer Black and Robert Litterman wrote an article on the Black-Litterman model. One intrinsic difference between the BLM and a traditional mean-average one is that, while the second provides the weights of the assets in a portfolio out of a optimization routine, the BLM has its starting point at the long-run equilibrium market portfolio(CAPM). Another highlighting point of the BLM is the ability to provide one clear structucture that is able to combine the long term equilibrium information with the investors views, providing a set of expected returns, which, together, will be the input to generate the weights on the assets. As far as the estimation process is concerned, and for the purpose of choosing the most appropriate model, it was taken into consideration the fact that the risk of a portfolio is determined by the covariation matrix of its assets and, being so, matrices with large dimensions play an important role in the analysis of investments. Whereas, provided the application under study, it is desirable to have a model that is able to carry out the analysis for a considerable number of assets. For these reasons, the Orthogonal GARCH was selected, once it can generate the matrix of covariation of the original system from just a few univariate volatilities, and for this reason, it is a computationally simple method. The orthogonal factors are obtained with principal components analysis. Decomposing the variance of the system into risk factors is highly important, once it allows the risk manager to focus separately on each relevant source of risk. The main idea behind the orthogonalization consists in working with a reduced dimension of components. In this kind of model, sufficient risk factors are considered, thus, the variability not perceived by the model will be considered insigficant noise to the system. Nevertheless, the precision, when not using all the components, will depend on the number of components be sufficient to explain the major part of the variability. Moreover, the model will provide reasonable results depending on principal component analysis performing properly as well, what will be more likely to happen, in highly correlated systems. It is worthy of note that the Orthogonal GARCH is equally useful and feasible when one intends to analyse a portfolio consisting of assets across various types of risk, it means, a system which is not highly correlated. It is common to have such a portfolio, with, for instance, currency rates, stocks, fixed income and commodities. In order to make it to perform properly, it is necessary to separate groups with the same kind of risk and then carry out the principal component analysis by group and then merge the covariance matrices, producing the covariance matrix of the original system. To work together with the orthogonalization method, the GARCH model was chosen because it is able to draw the main stylized facts which characterize financial time series. Stylized facts are statistical patterns empirically observed, which are believed to be present in a number of time series. Financial time series which sufficient high frequency (intraday, daily and even weekly) usually present such behavior. For estimating returns purposes, it was used a ARMA model, and together with the covariance matrix estimation, we have all the parameters needed to perform the BLM study, coming out, in the end, with the optimal portfolio in a given initial time. In addition, we will make forecasts with the GARCH model, obtaining optimal portfolio for the following weeks. We will show that the association of the BLM with the Orthogonal GARCH model can generate satisfactory and coherent with intuition results and, at the same time, keeping the model simple. Our application is on fixed income returns, more specifically, returns of bonds issued in the domestic market by the Brazilian National Treasury. The motivation of this work was to put together statistical tolls and finance uses and applications, more specifically those related to the bonds issued by the National Treasuy, which have become more and more popular due to the \"Tesouro Direto\" program. In conclusion, this work aims to bring useful information either for investors or to debt managers, once the mean-variance model can be useful for those who want to maximize return at a given level or risk as for those who issue bonds, and, thus, seek to reduce their issuance costs at prudential levels of risk.

Conselho Nacional de Desenvolvimento Científico e Tecnológico
Esta tese tem como foco os efeitos da desigualdade de renda na saúde bucal e as tendências em desigualdades socioeconômicas em saúde bucal. Qualquer injustiça social, pelo caráter moral é digna de estudo, porém nem toda desigualdade de renda é socialmente injusta. Ela se torna injusta quando as pessoas com menos recursos são aquelas que permitem que as desigualdades econômicas afetem direitos humanos, como o direito a um nível de vida que assegure ao indivíduo e a sua família uma vida saudável. As desigualdades de renda foram estudadas em duas vertentes:a) efeitos contextuais da desigualdade de renda na saúde bucal ; b) tendências na diferença de saúde bucal entre pessoas com maior e menor renda. A primeira parte contém quatro artigos originais que estudaram a associação e os mecanismos contextuais p elos quais a desigualdade de renda afeta a saúde bucal. Para isso, foram utilizados dados do inquérito em saúde bucal SBBrasil de 2002. Os resultados mostraram que: a) a associação entre desigualdade de renda e saúde bucal é mais forte em relação à cárie dental do que outras doenças bucais (e.g. doenças periodontais e maloclusões); b)seus efeitos estão mais fortemente associados à doenças bucais de menor latência; c) os efeitos associados à cárie dental afetam pobres e ricos igualmente; e d) a ausência de políticas públicas parece ser a melhor explicação para os efeitos da excessiva desigualdade de renda no Brasil. Ainda em relação às políticas públicas, foi encontrados que os ricos beneficiam-se mais de políticas públicas municipais do que os pobres. A segunda parte desta tese contém dois artigos originais que descrevem as tendências em saúde bucal e o uso dos serviços odontológicos em grupos de maior e menor renda, no Brasil e na Suécia. Para essas análises, foram usados dados dos inquéritos em saúde bucal no Brasil dos anos de 1986 e 2002, e para Suécia foram obtidos dados do "Swedish Level of Living Survey" para 1968, 1974, 1981, 1991 e 2000. As tendências relacionadas à prevalência de edentulismo mostraram que houve uma redução das desigualdade em percentuais absolutos nos dois países, porém, no Brasil houve um aumento das diferenças quando o desfecho foi a prevalência de nenhum dente perdido. As reduções das disparidades em edentulimo estiveram associadas à presença de uma diferença inicial significativa ,já o aumento das desigualdade na prevalência de nenhum dente perdido esteve relacionado a uma pequena desigualdade no início da coleta de dados. Em relação às desigualdades de uso dos serviços, ressalta-se que o grupo mais pobre permanece utilizando menos os serviços odontológicos em ambos os países e as diferenças continuam significantes através dos tempos. Entretanto, tanto no Brasil como na Suécia, essas diferenças reduziram levemente nas coortes jovens em função do declínio no percentual de pessoas mais ricas que visitam o dentista. Nossos dados permitem concluir que as desigualdades, em saúde bucal, mesmo em países altamente igualitários, como a Suécia.
This thesis focuses on the effect of income distribution on oral health and trends on socioeconomic disparities in oral health. Any social injustice, because of moral issues, is worth studying, though not all inequality of is unfair. Income inequality is unfair when people with less economic resources are penalized with poor health because of their condition of poverty. Unjust societies are those that allow economic inequalities to affect human rights as the right to a standard of living that ensures the individuals and their family a healthy life. Income inequalities were studied in two aspects: a) the contextual effects of income inequality in oral health, and; b) trends in the difference in oral health among people with higher and lower income. The first part contains 4 original articles that studied the association and the contextual mechanism by which income inequality affects oral health. For this we used data of the oral health survey SSBrasil in 2002. The results showed that: a) the association between income inequality and oral health is stronger in relation to dental caries than other oral diseases (e.g. periodontal diseases and malocclusions); b) the effects of inequality of income are more strongly associated with oral diseases of a shorter latency: c) that the effects associated with dental caries affect equally the rich and the poor. The second part of this thesis contains two original articles that described the trends in oral health and in the use of dental services into groups of higher and lower income, in Brazil and Sweden. For this analysis data were obtained from the Brazilian oral health surveys for the year 2002, while for Sweden were used data from the "Swedish Level of Living Survey" for the years 1968, 1974, 1981, 1991 and 2000. Trends in the prevalence of edentulismo showed a reduction in absolute disparities in both countries, but in Brazil trends in the prevalence of "no missing tooth" increased. Reductions in disparities in edentulismo were associated with the presence of a significant initiak difference, while the increase in inequality for outcome "no missing tooth" was related to small inequalities in the begining of data collection. Trends in the use of dental services highlighted that the poorer have been using less the dental services in both countries and the difference remain saignificant over time. however, in Brazil and Sweden, these differences decrease slightly in the cohort of young people because there was a decline in the percentage of rich people who visit the dentist. Our data show that income inequalities in oral health and use of dental serviceshave historically favored the more affluent population even in highly egalitarian countires as Sweden.

Avec l’accélération sociale de la « modernité tardive », de nouveaux enjeux politiques et économiques occupent une place de plus en plus importante dans les compositions territoriales, en les confrontant à une recomposition forte des temporalités qui affectent le monde vécu. La transformation numérique n’en est pas la cause mais s’inscrit dans cette dynamique « d’éphémérisation du présent » et la renforce vraisemblablement selon des modalités concrètes, à divers niveaux d’échelle. Il s'agit dans ce travail de comprendre comment les relations entre les formes commerciales et les formes spatiales sont recomposées, redessinées pas la mutation numérique, en étudiant, dans le cadre d'une CIFRE, les évolutions respectives des commerces et du territoire du centre-ville de Rennes. Le projet de recherche proposé ici vise à comprendre l'articulation entre les pratiques de la ville, les pratiques commerciales, les lieux et espaces, mais également les temporalités. Ce programme de recherches, s’inscrit de façon très large dans les problématiques « Entre formes et normes » de l’équipe PREFIcs. Il repose sur une conception étendue des logiques d’information et de communication qui considèrent que l’information, pour être mise en sens, symbolique, doit être également un processus de mise en forme, prenant en compte l’articulation des formes organisationnelles. Cette recherche questionne donc la reconfiguration de l’espace-temps, celle des sphères publiques et des affectations matérielles comme cadre pour les logiques commerciales et les imaginaires de consommation
Due to the social acceleration of "late modernity", new political and economic issues are taking more space in territorial compositions. Confronting them with a strong recomposition of temporalities that affect the lived world. The digital transformation is not the cause but is part of this dynamic "ephemeral present"? And is likely to strengthen it in concrete terms at various levels of scale. The aim of this work is to understand is to understand how the relations between commercial forms and spatial forms are recomposed, redrawn by the numerical mutation. By studying, within the framework of a CIFRE, the respective evolutions of the shops and the territory of Rennes’s city center. The current research program will help you understad the link between city practices, commercial practices, places and spaces, but also temporalities.This research program takes part of the "Between Form and Standards" program of the PREFIcs team. It is based on an extended conception of the logics of information and communication which consider that information, to make sens, symbolically, must also be a process of formatting, considering the articulation of organizational forms. This research paper therefore questions the reconfiguration in space and time, those of public spheres and material assignments as a framework for commercial logics and consumption imaginaries

A presente pesquisa visa analisar a dinâmica dos benefícios assistenciais do governo federal, buscando entender se a mesma se coaduna com a teoria dos ciclos eleitorais. Nesse sentido, foi avaliado se o número de concessões destes benefícios tenderia a crescer com a aproximação da eleições. Para atingir tal objetivo, foram utilizados dados mensais do número de concessões de três dos principais benefícios assistenciais brasileiros: o Benefício de Prestação Continuada, o Bolsa Família e o Auxílio Doença. Com base na análise das séries de tempo e dos dados em painel associados a estes últimos, foi possível detectar que a proximidade das eleições tende a afetar o número de concessões de benefícios assistenciais na maior parte dos casos analisados. Entretanto, a discussão dos resultados atingidos parece apontar no sentido de que os efeitos eleitorais encontrados não são tão somente resultados de manipulações eleitorais de políticos que visam à reeleição, mas frutos de uma dinâmica mais ampla, que seria característica de períodos eleitorais.
This research aims to analyze the dynamics of the welfare benefits of the federal government, seeking to understand whether it is consistent with the theory of electoral cycles. Accordingly, we assessed whether the number of concessions to these benefits tend to increase with the approaching elections. To achieve this, we used monthly data on the number of leases of three major Brazilian welfare benefits: the Benefício de Prestação Continuada, the Bolsa Família and Auxílio Doença. Based on the analysis of time series and panel data associated with the latter, it was possible to detect that the proximity of elections tends to affect the number of grants of welfare benefits in most cases analyzed. However, the discussion of the results indicate that the effects of elections are not solely the results of manipulations of politicians who seek reelection, but fruits of a wider dynamic that would be characteristic of elections.

La synthèse d'images, qui consiste à développer des algorithmes pour générer des images à l'aide d'un ordinateur, est devenue incontournable dans de nombreuses disciplines.

Les méthodes d'affichage interactives permettent à l'utilisateur d'explorer des environnements virtuels en réalisant l'affichage des images à une cadence suffisamment élevée pour donner une impression de continuité et d'immersion. Malgré les progrès réalisés par le matériel, de nouveaux besoins supplantent toujours les capacités de traitement, et des techniques d'accélération sont nécessaires pour parvenir à maintenir une cadence d'affichage suffisante. Ce travail s'inscrit précisemment dans ce cadre. Il est consacré à la problématique de l'élimination efficace des objets masqués, en vue d'accélérer l'affichage de scènes complexes. Nous nous sommes plus particulièrement intéressé aux méthodes de précalcul, qui effectuent les calculs coûteux de visibilité durant une phase de prétraitement et les réutilisent lors de la phase de navigation interactive. Les méthodes permettant un précalcul complet et exact sont encore hors de portée à l'heure actuelle, c'est pourquoi des techniques approchées leur sont préférée en pratique. Nous proposons trois méthodes de ce type.

La première, présentée dans le chapitre 4, est un algorithme permettant de déterminer de manière exacte si deux polygones convexes sont mutuellement visibles, lorsque des écrans sont placés entre eux. Nos contributions principales ont été de simplifier cette requête, tant du point de vue théorique que du point de vue de l'implémentation, ainsi que d'accélérer son temps moyen d'exécution à l'aide d'un ensemble de techniques d'optimisation. Il en résulte un algorithme considérablement plus simple à mettre en oeuvre que les algorithmes exacts existant dans la littérature. Nous montrons qu'il est également beaucoup plus efficace que ces derniers en termes de temps de calcul.

La seconde méthode, présentée dans le chapitre 5, est une approche originale pour encoder l'information de visibilité, qui consiste à stocker l'ombre que générerait chaque objet de la scène s'il était remplacé par une source lumineuse. Nous présentons une analyse des avantages et des inconvénients de cette nouvelle représentation.

Finalement, nous proposons dans le chapitre 6 une méthode de calcul de visibilité adaptée aux scènes d'intérieur. Dans ce type d'environnements, les graphes cellules-portails sont très répandus pour l'élimination des objets masqués, en raison de leur faible coût mémoire et de leur grande efficacité. Nous reformulons le problème de la génération de ces graphes en termes de segmentation d'images, et adaptons un algorithme classique, appelé «watershed», pour les obtenir de manière automatique. Nous montrons que la décomposition calculée de la sorte est proche de la décomposition classique, et qu'elle peut être utilisée pour l'élimination des objets masqués.

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

On peut atteindre des images réalistes par la simulation du transport lumineuse avec des méthodes de Monte-Carlo. La possibilité d’utiliser des sources de lumière réalistes pour synthétiser les images contribue grandement à leur réalisme physique. Parmi les modèles existants, ceux basés sur des cartes d’environnement ou des champs lumineuse sont attrayants en raison de leur capacité à capter fidèlement les effets de champs lointain et de champs proche, aussi bien que leur possibilité d’être acquis directement. Parce que ces sources lumineuses acquises ont des fréquences arbitraires et sont éventuellement de grande dimension (4D), leur utilisation pour un rendu réaliste conduit à des problèmes de performance.Dans ce manuscrit, je me concentre sur la façon d’équilibrer la précision de la représentation et de l’efficacité de la simulation. Mon travail repose sur la génération des échantillons de haute qualité à partir des sources de lumière par des estimateurs de Monte-Carlo non-biaisés. Dans ce manuscrit, nous présentons trois nouvelles méthodes.La première consiste à générer des échantillons de haute qualité de manière efficace à partir de cartes d’environnement dynamiques (i.e. qui changent au cours du temps). Nous y parvenons en adoptant une approche GPU qui génère des échantillons de lumière grâce à une approximation du facteur de forme et qui combine ces échantillons avec ceux issus de la BRDF pour chaque pixel d’une image. Notre méthode est précise et efficace. En effet, avec seulement 256 échantillons par pixel, nous obtenons des résultats de haute qualité en temps réel pour une résolution de 1024 × 768. La seconde est une stratégie d’échantillonnage adaptatif pour des sources représente comme un "light field". Nous générons des échantillons de haute qualité de manière efficace en limitant de manière conservative la zone d’échantillonnage sans réduire la précision. Avec une mise en oeuvre sur GPU et sans aucun calcul de visibilité, nous obtenons des résultats de haute qualité avec 200 échantillons pour chaque pixel, en temps réel et pour une résolution de 1024×768. Le rendu est encore être interactif, tant que la visibilité est calculée en utilisant notre nouvelle technique de carte d’ombre (shadow map). Nous proposons également une approche totalement non-biaisée en remplaçant le test de visibilité avec une approche CPU. Parce que l’échantillonnage d’importance à base de lumière n’est pas très efficace lorsque le matériau sous-jacent de la géométrie est spéculaire, nous introduisons une nouvelle technique d’équilibrage pour de l’échantillonnage multiple (Multiple Importance Sampling). Cela nous permet de combiner d’autres techniques d’échantillonnage avec le notre basé sur la lumière. En minimisant la variance selon une approximation de second ordre, nous sommes en mesure de trouver une bonne représentation entre les différentes techniques d’échantillonnage sans aucune connaissance préalable. Notre méthode est pertinence, puisque nous réduisons effectivement en moyenne la variance pour toutes nos scènes de test avec différentes sources de lumière, complexités de visibilité et de matériaux. Notre méthode est aussi efficace par le fait que le surcoût de notre approche «boîte noire» est constant et représente 1% du processus de rendu dans son ensemble
Realistic images can be rendered by simulating light transport with Monte Carlo techniques. The possibility to use realistic light sources for synthesizing images greatly contributes to their physical realism. Among existing models, the ones based on environment maps and light fields are attractive due to their ability to capture faithfully the far-field and near-field effects as well as their possibility of being acquired directly. Since acquired light sources have arbitrary frequencies and possibly high dimension (4D), using such light sources for realistic rendering leads to performance problems.In this thesis, we focus on how to balance the accuracy of the representation and the efficiency of the simulation. Our work relies on generating high quality samples from the input light sources for unbiased Monte Carlo estimation. In this thesis, we introduce three novel methods.The first one is to generate high quality samples efficiently from dynamic environment maps that are changing over time. We achieve this by introducing a GPU approach that generates light samples according to an approximation of the form factor and combines the samples from BRDF sampling for each pixel of a frame. Our method is accurate and efficient. Indeed, with only 256 samples per pixel, we achieve high quality results in real time at 1024 × 768 resolution. The second one is an adaptive sampling strategy for light field light sources (4D), we generate high quality samples efficiently by restricting conservatively the sampling area without reducing accuracy. With a GPU implementation and without any visibility computations, we achieve high quality results with 200 samples per pixel in real time at 1024 × 768 resolution. The performance is still interactive as long as the visibility is computed using our shadow map technique. We also provide a fully unbiased approach by replacing the visibility test with a offline CPU approach. Since light-based importance sampling is not very effective when the underlying material of the geometry is specular, we introduce a new balancing technique for Multiple Importance Sampling. This allows us to combine other sampling techniques with our light-based importance sampling. By minimizing the variance based on a second-order approximation, we are able to find good balancing between different sampling techniques without any prior knowledge. Our method is effective, since we actually reduce in average the variance for all of our test scenes with different light sources, visibility complexity, and materials. Our method is also efficient, by the fact that the overhead of our "black-box" approach is constant and represents 1% of the whole rendering process

Le nuage de points 3D est la donnée obtenue par la majorité des méthodes de numérisation surfacique actuelles. Nous nous intéressons ainsi dans cette thèse à l'utilisation de nuages de points comme unique représentation explicite de surface. Cette thèse présente deux contributions en traitements basés points. La première contribution proposée est une nouvelle méthode de rendu de nuages de points bruts et massifs par opérateurs pyramidaux en espace image. Cette nouvelle méthode s'applique aussi bien à des nuages de points d'objets scannés, que de scènes complexes. La succession d'opérateurs en espace image permet alors de reconstruire en temps réel une surface et d'en estimer des normales, ce qui permet par la suite d'en obtenir un rendu par ombrage. De plus, l'utilisation d'opérateurs pyramidaux en espace image permet d'atteindre des fréquences d'affichage plus élevées d'un ordre de grandeur que l'état de l'art .La deuxième contribution présentée est une nouvelle méthode de simulation numérique en mécanique des fluides en volumes immergés par reconstruction implicite étendue. La méthode proposée se base sur une nouvelle définition de surface implicite par moindres carrés glissants étendue à partir d'un nuage de points. Cette surface est alors utilisée pour définir les conditions aux limites d'un solveur Navier-Stokes par éléments finis en volumes immergés, qui est utilisé pour simuler un écoulement fluide autour de l'objet représenté par le nuage de points. Le solveur est interfacé à un mailleur adaptatif anisotrope qui permet de capturer simultanément la géométrie du nuage de points et l'écoulement à chaque pas de temps de la simulation
Most surface 3D scanning techniques produce 3D point clouds. This thesis tackles the problem of using points as only explicit surface representation. It presents two contributions in point-based processing. The first contribution is a new raw and massive point cloud screen-space rendering algorithm. This new method can be applied to a wide variety of data from small objects to complex scenes. A sequence of screen-space pyramidal operators is used to reconstruct in real-time a surface and estimate its normals, which are later used to perform deferred shading. In addition, the use of pyramidal operators allows to achieve framerate one order of magnitude higher than state of the art methods. The second proposed contribution is a new immersed boundary computational fluid dynamics method by extended implicit surface reconstruction. The proposed method is based on a new implicit surface definition from a point cloud by extended moving least squares. This surface is then used to define the boundary conditions of a finite-elements immersed boundary transient Navier-Stokes solver, which is used to compute flows around the object sampled by the point cloud. The solver is interfaced with an anisotropic and adaptive meshing algorithm which refines the computational grid around both the geometry defined by point cloud and the flow at each timestep of the simulation

Du fait de l'importance accrue des personnages virtuels dans tous les secteurs du loisir numérique, la
simulation de chevelures est devenue, ces dernières années, un thème de recherche très actif en informatique graphique. Par ailleurs, la simulation physique de cheveux attire de plus en plus l'attention des cosmétologues, qui voient dans le prototypage virtuel un moyen efcace pour mettre au point des produits capillaires.
Cette thèse s'attaque à deux grandes difcultés antagonistes liées à la simulation de chevelures : d'une part, la simulation en temps interactif d'une chevelure complète ; d'autre part, le réalisme physique de la forme et du mouvement d'une chevelure.
Dans un premier temps, nous élaborons de nouveaux algorithmes visant à réduire le coût de calcul inhérent
aux méthodes classiques d'animation de chevelures. Nos approches exploitent pour la première fois l'animation multi-résolution et le rendu volumique de longs cheveux, donnant lieu à des simulations interactives.
Dans un second temps, nous proposons un modèle physiquement réaliste de chevelure, réalisé en collaboration avec des spécialistes en modélisation mécanique et en cosmétologie. Nous présentons tout d'abord le modèle mécanique précis de cheveu unique, issu de la théorie de Kirchhoff sur les tiges élastiques, dont nous avons participé à l'élaboration au cours de ce partenariat. Étendu à l'échelle de la chevelure complète, ce modèle est ensuite appliqué à la génération réaliste de coiffures naturelles tatiques, puis à la simulation dynamique de chevelures d'origines ethniques variées, avant d'être nalement validé à travers un ensemble de comparaisons avec le réel.

De nombreuses études ont été menées lors des vingt dernières années dans le domaine de l'auralisation.Elles consistent à rendre audible les résultats d'une simulation acoustique. Ces études se sont majoritairementfocalisées sur les algorithmes de propagation et la restitution du champ acoustique dans desenvironnements complexes. Actuellement, de nombreux travaux portent sur le rendu sonore en tempsréel.Cette thèse aborde la problématique du rendu sonore dynamique d'environnements complexes selonquatre axes : la propagation des ondes sonores, le traitement du signal, la perception spatiale du son etl'optimisation informatique. Dans le domaine de la propagation, une méthode permettant d'analyser lavariété des algorithmes présents dans la bibliographie est proposée. A partir de cette méthode d'analyse,deux algorithmes dédiés à la restitution en temps réel des champs spéculaires et diffus ont été extraits.Dans le domaine du traitement du signal, la restitution est réalisée à l'aide d'un algorithme optimisé despatialisation binaurale pour les chemins spéculaires les plus significatifs et un algorithme de convolutionsur carte graphique pour la restitution du champ diffus. Les chemins les plus significatifs sont extraitsgrace à un modèle perceptif basé sur le masquage temporel et spatial des contributions spéculaires.Finalement, l'implémentation de ces algorithmes sur des architectures parallèles récentes en prenant encompte les nouvelles architectures multi-coeurs et les nouvelles cartes graphiques est présenté.

碩士
國立臺灣大學
電機工程學研究所
95
This thesis is focused on the construction of physical dynamic system about the ship modeling and motion simulation on virtual reality. We introduce the deep ocean surface constructed as our virtual environment in real-time by personal computer which is mounted NVIDIA GeForce Go 7400 graphics card and 2.00GHz CPU. We introduce an ocean spectrum theorem, so the ocean wave is created by defining the gravity and the wind. Further more, in order to obtain the real-time and realistic rendering ocean scenery, we adopt Graphics Processor Unit (GPU) hardware on shading color. The reflection phenomenon and Fresnel effect are concerned on our dynamic ocean. On ship modeling, the forces and torques are calculated from the generated dynamic waves, which are based on the hydrodynamics and transferred to our ship model. We present a new algorithm to assign points on ship hull, and apply the 3D mathematics theorem to locate each point. According to the calculation of the volume of ship below the ocean surface, we can approach the dynamics of the ship. This simulation can also be integrated with the 6 degree-of-freedom motion platform to generate realistic motion sensation.

On retrouve dans la nature un nombre impressionnant de matériaux semi-transparents tels le marbre, le jade ou la peau, ainsi que plusieurs liquides comme le lait ou les jus. Que ce soit pour le domaine cinématographique ou le divertissement interactif, l'intérêt d'obtenir une image de synthèse de ce type de matériau demeure toujours très important. Bien que plusieurs méthodes arrivent à simuler la diffusion de la lumière de manière convaincante a l'intérieur de matériaux semi-transparents, peu d'entre elles y arrivent de manière interactive. Ce mémoire présente une nouvelle méthode de diffusion de la lumière à l'intérieur d'objets semi-transparents hétérogènes en temps réel. Le coeur de la méthode repose sur une discrétisation du modèle géométrique sous forme de voxels, ceux-ci étant utilisés comme simplification du domaine de diffusion. Notre technique repose sur la résolution de l'équation de diffusion à l'aide de méthodes itératives permettant d'obtenir une simulation rapide et efficace. Notre méthode se démarque principalement par son exécution complètement dynamique ne nécessitant aucun pré-calcul et permettant une déformation complète de la géométrie.
We find in nature several semi-transparent materials such as marble, jade or skin, as well as liquids such as milk or juices. Whether it be for digital movies or video games, having an efficient method to render these materials is an important goal. Although a large body of previous academic work exists in this area, few of these works provide an interactive solution. This thesis presents a new method for simulating light scattering inside heterogeneous semi-transparent materials in real time. The core of our technique relies on a geometric mesh voxelization to simplify the diffusion domain. The diffusion process solves the diffusion equation in order to achieve a fast and efficient simulation. Our method differs mainly from previous approaches by its completely dynamic execution requiring no pre-computations and hence allowing complete deformations of the geometric mesh.

L'imagerie moderne générée par ordinateur cherche constamment à être de plus en plus représentative de la réalité physique tout autour de nous, et un de ces phénomènes clés est la notion d'effets de distribution. Les effets de distribution sont une catégorie de comportements du transport de la lumière caractérisés par leur nature distribuée selon une ou plusieurs dimension(s) donnée(s). Par exemple, le flou de mouvement est un effet de distribution dans le temps, alors que la profondeur de champ introduit le diaphragme de la caméra, ajoutant ainsi deux dimensions. Ces effets sont communs dans les films et la réalité, les rendant donc désirables à reproduire. Dans cette thèse par articles, nous présentons quatre articles qui utilisent, étendent ou s'inspirent des effets de distribution. Premièrement, nous proposons une technique novatrice pour faire le rendu de flou de mouvement non-linéaire pour des applications en temps réel tout en conservant des caractéristiques clés d'efficacité et de mise à l'échelle. Nous tirons avantage des courbes de Bézier pour concevoir une approximation de mouvement non-linéaire depuis seulement quelques images clés et rastérisons une géométrie synthétisée pour reproduire le mouvement. Deuxièmement, nous présentons un algorithme qui fait le rendu de matériaux scintillants à haute fréquence illuminés par de grandes cartes environnementales. En utilisant une combinaison d'un système d'histogrammes de mi-vecteurs compact et des harmoniques sphériques multi échelle, nous pouvons efficacement représenter des normales de surface denses et rendre leurs interactions avec des sources de lumière filtrées de grandes dimensions. Troisièmement, nous introduisons une nouvelle méthode pour faire le rendu de dispersion sous la surface en tirant avantage de l'analyse fréquentielle et du parcours d'un arbre dual. En calculant le transport de la lumière sous la surface en espace image, nous pouvons rapidement analyser la fréquence du signal et déterminer des bandes passantes efficaces que nous pouvons alors utiliser pour limiter notre traversée dans un arbre dual d'ombrage et d'illumination. Finalement, nous démontrons un algorithme novateur d'illumination globale diffuse en temps réel qui utilise des sondes d'irradiance dynamiques. Grâce à des mises à jour efficaces de distribution de radiance, nous pouvons mettre à jour des sondes d'irradiance pendant l'exécution, prenant en compte les objets dynamiques et une illumination changeante, et nous le combinons avec une requête d'irradiance filtrée plus robuste, rendant une grille de sondes d'irradiance dense traitable en temps réel avec des artefacts minimes.
Modern computer generated imagery strives to be ever more faithful to the physical reality around us, and one such key physical phenomenon is the notion of distribution effects. Distribution effects are a category of light transport behaviors characterized by their distributed nature across some given dimension(s). For instance, motion blur is a distribution effect across time, while depth of field introduces a physical aperture for the camera, thus adding two more dimensions. These effects are commonplace in film and real life, thus making them desirable to reproduce. In this manuscript-based thesis, we present four papers which leverage, extend or inspire themselves from distribution effects. First, we propose a novel technique to render non-linear motion blur for real-time applications while conserving important scalability and efficiency characteristics. We leverage Bézier curves to approximate non-linear motion from just a few keyframes and rasterize synthesized geometry to replicate motion. Second, we present an algorithm to render glinty high-frequency materials illuminated by large environment maps. Using a combination of a compact half-vector histogram scheme and multiscale spherical harmonics, we can efficiently represent dense surface normals and render their interaction with large, filtered light sources. Third, we introduce a new method for rendering subsurface scattering by taking advantage of frequency analysis and dual-tree traversal. Computing screen-space subsurface light transport, we can quickly analyze signal frequency and determine efficient bandwidths which we then use to limit our traversal through a shading/illumination dual-tree. Finally, we show a novel real-time diffuse global illumination scheme using dynamically updated irradiance probes. Thanks to efficient spherical radiance distribution updates, we can update irradiance probes at runtime, taking into consideration dynamic objects and changing lighting, and combine it with a more robust filtered irradiance query, making dense irradiance probe grids tractable in real-time with minimal artifacts.